Diabetes mellitus is a disease of major global importance, increasing in frequency at almost epidemic rates, such that the worldwide prevalence in 2006 is 170 million people and is predicted to at least double over the next 10-15 years. Diabetes is characterized by a chronically raised blood glucose concentration (hyperglycemia) due to a relative or absolute lack of the pancreatic hormone, insulin. Generally, normal pancreatic islet cells (beta cells) continuously sense the blood glucose levels and consequently regulate insulin secretion to maintain near constant glucose levels.
Diabetes mellitus patients require the administration of varying amounts of insulin throughout the day to control their blood glucose levels. In recent years, ambulatory portable insulin infusion pumps have emerged as a superior alternative to multiple daily injections of insulin. These pumps, which deliver insulin at a continuous basal rate as well as in bolus volumes, were developed to liberate patients from repeated self-administered injections, and allow greater flexibility in dose administration. Both basal and bolus volumes have to be delivered in precise doses, according to individual prescription, since an under or overdose of insulin could be fatal. Therefore, insulin injection pumps have to provide high reliability to prevent delivery of an unintentional insulin excess or shortage.
Several ambulatory insulin infusion devices are currently available on the market. The first generation of disposable syringe-type reservoirs and tubes are described, for example, in U.S. Pat. Nos. 2,631,847, 3,771,694, 4,657,486, and 4,544,369, the contents of which are hereby incorporated by reference in their entireties. Generally, the reservoirs of these devices are symmetrical, round, and tubular-shaped, and have rigid walls to enable smooth movement of the pump piston (plunger) and to maintain proper sealing.
Some of the drawbacks of these devices include their large size and weight, caused by the spatial configuration and the relatively large driving mechanism of the syringe and the piston. The relatively bulky devices have to be carried in a patient's pocket or be attached to the patient's belt. Consequently, the fluid delivery tube is long, usually longer than 60 cm, to enable needle insertion in remote sites of the body. These uncomfortable bulky fluid delivery devices with long tubing are not popular with the majority of diabetic insulin users, because these devices interfere with regular activities, such as sleeping and exercising (e.g., swimming). Furthermore, the effect of the image projected on a teenagers' body is unacceptable among teenagers. In addition, the use of a long delivery tube excludes some optional remote insertion sites, like the buttocks and the extremities.
To avoid tubing limitations, a second generation of pumps has been developed. These pumps include a housing having a bottom surface adapted for attachment to the user's skin, a reservoir disposed within the housing, and an injection needle adapted to be in fluid communication with the reservoir. These skin adhered devices typically are discarded of every 2-3 days, similarly to the infusion sets employed with the pumps of the first generation. Such second generation devices are described, for example, in U.S. Pat. Nos. 4,498,843, 5,957,895, 6,589,229, and 6,740,059, the contents of which are hereby incorporated by reference in their entireties. Other configurations of skin-secured pumps are disclosed, for example, in U.S. Pat. Nos. 6,723,072 and 6,485,461, the contents of which are hereby incorporated by reference in their entireties. The reservoirs of such devices, like the reservoirs used in 1st generation pumps, are usually tubular and syringe like, thus requiring a relatively large occupying space and a thick housing.
To address the volume and cost constraints, a 3rd generation skin-secured pump was proposed as described, for example, in commonly-owned patent applications PCT/IL06/001276 (Publication No. WO 2005/052277), entitled “Modular portable Infusion Pump” and U.S. patent application Ser. No. 11/397,115, entitled “Systems and methods for sustained medical infusion and devices related thereto”, filed Apr. 3, 2006, the contents of which are hereby incorporated by reference in their entireties. Various embodiments of the device include some or all of the following components:                1—A dispensing patch unit—the dispensing patch unit includes two parts, a disposable part and a reusable part. The reusable part generally includes electronic components and the metering portion. The disposable part generally includes a reservoir for therapeutic fluid, a short delivery tube and an exit port. Buttons on the reusable part enable manual bolus delivery and/or specifying other commands and control operations. After connection of the reusable and disposable parts, the assembled device has a very thin dimension, rendering the whole device inexpensive, light and discrete.        2—A remote control unit for data acquisition, programming, and communication of user input.        3—A cradle unit—a skin securable piece with, for example, adhesive that is connected to the skin and enables connection and disconnection of the dispensing patch unit.        4—A cannula cartridge unit—a cannula and a penetrating member are shielded within a protecting case. The cartridge can be loaded into an automatic inserter that fires the cannula into the body through a cradle opening.        